Artificial tooth



April 3, 1962 R. sTRAcK 3,027,642

ARTIFICIAL TooTH Filed Feb. 5, 1958 7a I INVENTOR W .f 19W United StatesPatent hfice 3,0*27,64Z Patented Apr. 3, 1962 3,027,642 ARTIFICIAL TOOTHRainer Strack, Pforzheim, Germany, assignor to Firma Tersa A.G., Biel,Switzerland Filed Feb. 5, 1958, Ser. No. 713,336 Claims priority,application Germany Feb. 7, 1957 2 Claims. (Cl. 32-8) The inventionrelates to a tooth with cusps (posterior tooth) for dental prostheticwork.

Cinematic survey about 'the spatial movements of the lower jaw againstthe unmovable upper jaw have shown that the natural movements, caused bymuscles and refiexes do not consist, as assunied up to now, of aprognatic bite, a lateral vbite which can be left or right, and aprogenic bite. As a rule, the progenic and the prognatic bite will notbe vfound during the normal masticatory movement 'but can only beproduced by intention or by coercion. They will only be found as acomponent in a lateral movement. But even this kind of lateral biteshows a fundamental different course as the one used in combination withprognatic and progenic bites, which have been employed as a base for theconstruction of the customary artificial teeth.

The construction of artificial teeth must be adapted to nature at leastas far as the natural movements of the jaws are considered as impulse,otherwise the cusps of the teeth will 'be a hndrance to thesesmooth-gliding movements, with the result that the dentures which haverelatively little attachment to the mucous membranes will tilt veryeasily. In order to avoid this inconvenience it has been necessaryheretofore to do quite a lot of corrective work on the teeth of thedenture if said denture was constructed in customary procedure and thisin order to adapt the final prosthetic work to the jawss naturalmovement. This usually meant that the cusps of the posterior teeth wereremoved and this in turn meant a reduction of the masticatory value ofthe denture, at the same time this meant that the initial presence ofcusps was quite illusionary. This grinding-in of the customaryartificial teeth once the denture was ready for wearing, was consideredabsolutely necessary in normal prosthetic work.

Up to now, the conception was, that the reflectory lateral movements ofthe jaws natural movement took place through an alternating rotation ofthe lower jaw and this around two definite axes in the space, situatedbehind the two condylic joints. Accordingly there are customary devicesfor the manufacture of artificial posterior teeth in which the movementsto the left and to the right are obtained by rotating the mechanicalpart representing the lower jaw, around two axes. Tests made on naturaljaws have proved that this is an erroneous assumption. The path of themandibulary movements in the space-With a fixed maxillary-should ratherbe considered as a nearly true translation to the side, the front anddownwards, to this must be added a slight rotation of the lower jaw, dueto the minute difference in the movements of the two condyles. In thiscase "translation" is understood as a displacement parallel to itself.

Free movements and a high masticatory effect is not all that is neededin a denture, there are also other demands, such as: easy speech,possibility to transport food freely from one side to the other, an easyflow of saliva etc. It is therefore necessary to shape or to form thetooth also in such a way as to have a resem'blance to a natural toothform. The artificial posterior tooth, object of this invention, has asnow known, one or more pyramidc occlusal cusps, and said cusps willpenetrate stereometrically in certain parts of the correspondingtooth-or the corresponding teethin which they have been built in. Toobtan this, another characterization of the tooth claimed in thisinvention, is the fact, that each pyramidic stump will show at leastfour sides, said sides to serve for the sliding-in of the cusps of theopposite side into the grooves which have been formed automaticallybetween the pyramidic stumps and this slidingin is due to a translativesidewards movement. There- -fore the tooth claimed in this inventiondfers fundarnentally from the customary and known artificial tooth basedon findings-now proved as being erroneous-that the lower jaw is makingprincipally a rotary movement instead of a translation movement and thiseven when moving sidewards.

The object of this invention is to provide means to increase thecapacity of artificial teeth to grind or to crush food by producing onthe occlusal surface of the artificial teeth sharp, definitely formedfacets and that such facets will become effective during the translationmovement, whereby the efiiciency of natural or artificiai teeth willeven be surpassed and at the same time the shape and the position of thecusps on the occlusal side of the teeth shall be arranged in such amanner, that once the den-` ture is in a correct position in the mouth,all movements will be possible without any obstruction or interceptionfrom said cusps.

The novel features which are considered as characteristic lfor theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation together with additional objects and advantag-es thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawing, inwhich:

FIG. 1 is a perspective view of an artificial back tooth according tothe present invention;

FIG. 2 is a schematic top view of the tooth shown in FIG. 1 and drawn toan enlarged scale;

FIG. 3 is a schematic perspective view of the cusps or pyramids formedon the occlusal surface of the tooth.

of the present invention;

ment of opposite back teeth according to the present invention inrelation to other teeth; and

FIG. 5 schematically illustrates the chewing action obtained betweenupper and lower teeth according to the present invention.

Referring now to the drawing and particularly to FIG. l of the same, itwill be seen that the artificial back tooth according to the presentinvention comprises a plurality of cusps on the occlusal surfacethereof, and each of these cusps has substantially the form of aquadrilateral pyramid P.

The arrangement is more clearly illustrated in FIGS. 2 and 3, whichrespectively show a top view of the occlusal surface of the tooth T' anda perspective view of the cusps or pyramids arranged thereon. As can beseen -from FIG. 2, the artificial tooth T according to the presentinvention has an occlusal upper surface OS for' masticating engagementwith an opposite tooth, and the artificial tooth T comprises a pluralityof cusps on the occlusal surface OS thereof, and each of the cusps has aplurality of facets F defining a quadrilateral pyramid P. The facets ofeach pyramid P intersect each other along lines respectively located intwo planes, indicated for the pyramid P at the left lower corner of thetooth T, as viewed in FIG. 2, by the lines B B and O C. The planeextending along the line B B is parallel to the side face SF of thetooth T, whereas the other plane is substantially normal to the sideface SF. Adjacent pyramids P are arranged with respect to each other insuch a manner that they engage and interpenetrate each other only atcorner portions thereof, so as to form grooves G therebetween. Each ofthe grooves G between adjacent pyramids P has its` highest point H inthe plane of intersection passng through the apices A of the adjacentpyramids and these grooves G extend downwardly inclined from the highestpoint H to opposite sides of the aforementioned plane.

According to the present invention the cusps and grooves on the occlusalsurface of the tooth are not simply a copy of the occlusal surfacearrangement of natural teeth, but the cusps and grooves of theartificial tooth according to the present invention are arranged toprovide for an improved masticating action. At the very instant when theteeth of the lower denture contact' the corresponding teeth of ltheupper jaw, edges and peaks of definitely constructed cusps in the lowerjaw will touch or contact corresponding definitely constructed edges andpeaks of the upper teeth of the denture. PIG. 4 shows a plurality ofteeth in this situation as seen from the side and FIG. 5 as seen 'fromthe front. During the masticating action and lateral translatorymovement lof the teeth T with respect to each other, correspondingplanes or facets of opposite teeth will slide closely along each otheras indicated by the arrows in PIG. S, to produce thus a maximum cuttngeffect and a maximum crushing effect on food particles 20 locatedbetween the teeth. By adapting the cusps or pyramids P and the grooves Gtherebetween, to the natural movement of the jaws, the teeth arearranged in such a manner that free movement of the cusps in one row ofteeth through the grooves of the opposite row of teeth is possible.

It will be understood |that each of the elements described above or twoor more together, may also find a useful application in other types ofartificial teeth differing from the types described above.

While the invention has been illustrated and described as embodied in anartificial tooth having a plurality of c-usps on the occlusal surfacethereof, it is not intended to 'be limited to the details shown, sincevarious modifications and strnctural changes may be made withoutdeparting in any way from the spirit of the present invention.

Without further analysis the foregong will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omtting features that,from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic or specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed and desired to `be secured by Letters Patent is:

1. An artificial back tooth having an occlusal surface for masticatingengagement with an opposite tooth, said artificial tooth comprising aplurality of cusps on the occlusal surface thereof, each of said cuspshaving a plurality of facets jointly defining a quadrilateral pyramid,the facets of each pyramid intersecting veach other along linesrespectively located in two planes one of which is substantially normaland the other substantially parallel to one side face of the tooth andadjacent pyramids engaging each other only at corner portions thereof.

2. An artificial 'back tooth having an occlusal surface for masticatingengagement With an opposite tooth, said artificial tooth comprisng aplurality of cusps on the occlusal surface thereof, each of said cuspshaving a plurality of facets jointly defining a quadrilateral pyramid,the facets of each pyramid intersecting each other along linesrespectively located in two planes one of which is substantially normaland the other snbstantially parallel to one side face of said tooth andadjacent pyramids engaging and interpenetrating each other only atcorner portions thereo'f so as to form grooves therebetween, each groovebetween adjacent pyramids having its highest point in the plane ofintersection passing through the apices of said adjacent pyramids andextending downwardly inclned from vthe highest point to opposite sidesof said plane.

References Cited in the file of this patent UNITED STATES PATENTS1,665,357 Gysi Apr. 10, 1928 2,1l5,1l6 McGrane Apr. 26, 1938 2,404,327Tighe July 16, 1946 2,603,869 Bjorklund July 22, 1952 2,688,800 GerberSept. 14, 1954

